Loader

ABSTRACT

A loader comprises an articulating frame arrangement for providing an articulating steering. The loader comprises a lifting arrangement mounted to a front frame portion of the frame arrangement. The lifting arrangement comprises an equipment connector at a distal end of the lifting arrangement, a main actuation system for moving the equipment connector between a lowered position and a lifted position, and an auxiliary actuation system for storing energy during lowering. The auxiliary actuation system uses the stored energy to support the main actuation system in raising of the equipment connecter. The auxiliary actuation system comprises an auxiliary actuator connected at one end to the front frame portion of the frame arrangement and connected at another end to the lifting arrangement at a transversal side of the lifting arrangement.

TECHNICAL FIELD

The present invention relates to a loader. The loader may be a wheel loader and comprise an electric drive system.

BACKGROUND OF THE INVENTION

Wheel loaders may comprise an articulating frame arrangement comprising a front frame portion and a rear frame portion, which are articulatingly interconnected for providing an articulating steering, and a lifting arrangement with a bucket for lifting material or earth from the ground to release it at a higher position, e.g. for dumping it in a dump truck. Wheel loader operations are energy intensive. Accordingly, one of the major factors of the operation costs of a conventional wheel loader is its energy consumption in the form of fuel. Another major factor for the operation costs are maintenance costs, e.g. for replacing or repairing moveable parts. EP 3 051 031 B1 describes a wheel loader with a lifting arrangement with enhanced loading and lifting capacity. Furthermore, it is known in the art to provide an additional cylinder above the main arm of the lifting arrangement of the wheel loader to recuperate energy during lowering of the main arm. This may allow for a reduction in energy consumption of the wheel loader.

SUMMARY

The present invention relates to a loader having a frame arrangement and a lifting arrangement. The loader may be a wheel loader. Additionally or alternatively, the loader may comprise tracks. The frame arrangement may comprise a front frame portion and a rear frame portion, which may be articulatingly interconnected for providing an articulating steering. Preferably, at least one axis with a set of wheels is mounted to each of the frame portions, wherein the axes may be rigid axes. The wheel loader may thus be a wheel loader with an articulating frame arrangement. Alternatively, the loader may be a skid steer loader, a compact track loader or any other type of loader. The loader comprises a lifting arrangement, the lifting arrangement being mounted to the frame arrangement, optionally to a front frame portion of the frame arrangement. The lifting arrangement comprises an equipment connector at its distal end, to which an equipment, e.g. a bucket, can be attached. Further, the loader comprises a main actuation system for pivoting the equipment connector relative to the frame arrangement such that the equipment connector is movable between a lowered position and a lifted position. This may also be referred to as lifting/raising and lowering of the lifting arrangement, respectively. Accordingly, the lifting arrangement allows the loader to move material and/or earth between a lowered and a lifted position, which is higher above the ground than the lowered position. For example, the loader may gather earth and/or material from the ground and dump it into the bed of a truck.

In a horizontal plane, the lifting arrangement may be rigidly mounted to the frame arrangement. Thus, the lifting arrangement, in particular the equipment connector, may not be adjustable in its orientation relatively to the frame arrangement in such a horizontal plane. However, the orientation of the equipment connector in said horizontal plane may be adjustable by steering of the loader, in particular by pivoting the front frame portion relative to the rear frame portion. At least a part of the lifting arrangement, in particular the equipment connector, may be moved upwards against gravity and downwards in the gravity direction, which will also be referred to as lifting/raising and lowering of the lifting arrangement and/or the equipment connector. For example, the equipment connector may be arranged at a distal end of a pivotal boom of the lifting arrangement, wherein the boom is pivotably attached to the frame arrangement, in particular a front frame portion, with its proximal end. Preferably, the pivot axis of such a boom extends parallel to a horizontal plane, in particular essentially orthogonally to a forward-backward direction and/or parallel to a left-right direction of the loader. The forward-backward direction may be defined by the frame arrangement when the loader is driven straight forward. In the straight driving direction, a front and a rear frame portion of the loader may be aligned with each other.

The loader may further comprise an auxiliary actuation system for storing energy during lowering of the equipment connecter and for using the stored energy to support the main actuation system in raising of the equipment connecter. The auxiliary actuation system may function as a recuperation system. The stored energy may be potential energy freed during lowering of part of the lifting arrangement, in particular during lowering of the equipment connector. The auxiliary actuation system therefore provides an energy recuperation during a corresponding actuation of the lifting arrangement driven by the main actuation system. The recuperation may be a fluid-operated recuperation, for example, a hydraulic and/or pneumatic energy recuperation. Correspondingly, the auxiliary actuation system may be configured as a fluid-operated system, in particular a hydraulic and/or pneumatic system. Optionally, the auxiliary actuation system does not require or comprise a motor or other form of energized pressure source. Accordingly, the auxiliary actuation system is simple and easy to service while being able to greatly increase efficiency of the loader. In particular, energy requirements during raising and lowering of the lifting arrangement may be reduced. Further, since the auxiliary system supports raising the lifting arrangement, other systems for actuation, such as the main actuation system, may be designed for a lower maximum load. The auxiliary actuation system may provide a counterbalanced lifting arrangement design. The auxiliary actuation system may also be called a recuperation and actuation system. The recuperation may avoid or reduce an increase in temperature in a hydraulic fluid of a hydraulic main actuation system during lowering of the lifting arrangement since hydraulic breaking of the boom movement during lowering with the main hydraulic actuation system may be avoided or reduced.

The auxiliary actuation system may further comprise an auxiliary actuator connected with its proximal end to the frame arrangement, e.g. to a front frame portion of the frame arrangement, and connected with its distal end to the lifting arrangement at a transversal side of the lifting arrangement. Such an arrangement is sturdy, compact and provides easy access for maintenance. In addition, the arrangement at a transversal side of the lifting arrangement is very unobstructive to a view of the operator of the loader. In particular, the operator may still easily see the equipment connector and/or any equipment connected thereto in a raised position and/or lowered position of the lifting arrangement. This facilitates operation of the loader. By comparison, an auxiliary actuator mounted above and/or on top of a boom of the lifting arrangement may be more obstructive, thus making it very difficult for the operator of such a loader to dump and/or gather materials at the correct location.

The frame arrangement, e.g. the front frame portion and the rear frame portion, may have a longitudinal extension that corresponds to the straight driving direction of the loader. A transversal side of the lifting arrangement may face in a direction transversal, preferably orthogonally, to the straight driving direction and/or a longitudinal extension of the frame arrangement. The transversal side of the lifting arrangement may face in a direction essentially corresponding to an axis direction of the front wheels of the loader. The transversal side of the lifting arrangement may further be oriented in parallel to a plane, in which the equipment connector of the lifting arrangement is moved from the lowered position to the lifted position, such that a normal onto said transversal side of the lifting arrangement is also a normal on said plane.

In an embodiment of the loader, the auxiliary actuator, in particular its distal end, is arranged below an operator's cab of the loader and/or a front window of the operator's cab, e.g. a bottom edge of the front window, in particular when the equipment connector is in its lowered position. This may improve the view of the operator on the equipment during operation of the lifting arrangement. The operator's cab may be provided at a rear frame portion of the frame arrangement of the loader. Alternatively or additionally, in an embodiment of the loader, the proximal end of the auxiliary actuator is connected to the frame arrangement, e.g. the front frame portion, at a position, which is provided below the operator's cab and/or the front window, e.g. the bottom edge of the front window, of the operator's cab. This may additionally improve visibility for the operator on the equipment and lifting arrangement during operation. Further, this may result in a compact and reliable design.

In an embodiment of the loader, the auxiliary actuation system is a fluid-operated actuation system, preferably comprising an accumulator for storing of energy. A fluid-operated actuation system may provide a large power output, transmit strong forces for lifting heavy loads, be very rigid, easy to repair and require only minimal maintenance. Alternatively or additionally, the main actuation system may also be a fluid-operated system. This may reduce overall complexity and allows using similar or identical parts both for the main and auxiliary actuation system. For example, the fluid may be a gas, e.g. nitrogen, and/or hydraulic oil. A fluid-operated accumulator is a reliable and simple energy storage device. The accumulator and auxiliary actuator may be fluidically connected to each other. In particular, the accumulator and actuator may be connected with a fluid line, which is configured to conduct pressurized fluid, such as oil or gas. Pressurization of the accumulator may involve compressing a medium of the fluid-operated system, such as a fluid or gas. However, pressurization may, for example, alternatively or additionally involve deforming an elastic part of the accumulator, such as a membrane, to store energy in the auxiliary system.

In an embodiment of the loader, the auxiliary actuation system is separate from the main actuation system, wherein the auxiliary actuation system is configured to store energy and to support raising of the equipment connector completely autonomously without any interaction with the main actuation system. Preferably, this system does not comprise a power supply for its actuation. It may be supplied with power from the main actuation system unit upon activation and then work autonomously therefrom. In particular, the auxiliary actuation system may work passively, in particular after an initial pressurization, and/or independently of the energy supply of the main actuation system. The separate fluid-operated auxiliary system is configured to store potential energy during lowering of the lifting arrangement and to use the stored energy to support raising of the lifting arrangement, wherein the auxiliary actuation system is configured to store the energy and to support raising of the lifting arrangement completely autonomous without any interaction with the main actuation system. In other words: The auxiliary actuation system is configured to store potential energy freed during lowering of the lifting arrangement and to use the stored energy to support raising of the lifting arrangement independently from the main actuation system.

In an embodiment of the loader, the main actuation system is an electrical system with an electrical power storage unit and an electrical drive configured to actuate movement of the equipment connector between the lowered and lifted position. The main actuation system may comprise an electric motor and/or an electrical energy storage device, such as a rechargeable battery. An electrical main actuation system may be very silent and environmentally friendly. The main electrical actuation system may be configured to move the lifting arrangement with an electric motor or may first convert the electric energy provided by the storage unit into another energy form, in particular hydraulic energy. The power storage unit is preferably a battery, in particular a rechargeable battery. The main electrical actuation system may also be configured for driving the loader, for example by turning wheels of the loader. Preferably, the electrical energy provided by the power storage unit is directly converted into kinetic energy moving the wheels of the loader. Alternatively, the wheels may be moved via a hydraulic system powered by an electrical motor, which is in turn powered by energy of the power storage unit. Preferably, the loader does not comprise means to generate electrical energy for the main electrical actuation system, such as a combustion engine. Instead, it may only rely on the electrical power storage unit for providing its operating power. Furthermore, the main electrical actuation system may be configured to actuate a steering of the loader by tiling the front frame portion and the rear frame portion with respect to each other.

In an embodiment of the loader, the main actuation system comprises a main hydraulic system configured to actuate movement of the equipment connector between the lowered and the lifted position, the main hydraulic system being powered by the electrical drive. For example, the electrical drive of the main actuation system may be configured to pressurize a main hydraulic system, for example by driving a hydraulic pump with the electrical drive. Transforming electrical energy into hydraulic pressure may be very efficient and allows for a compact design. In particular, this may allow for high maximum loads with a rather small electrical drive. Alternatively, the electrical drive may actuate the lifting arrangement directly without any energy conversion therebetween.

An underlying idea of the loader according to the present invention is to combine an efficient electrical system with an efficient hydraulic and/or pneumatic recuperation system to provide an efficient and simple loader. Surprisingly and contrary to what a person skilled in the art expects, such a combination of two systems working with different power transmissions principles may overall reduce complexity of the loader, simplify maintenance and increase efficiency. By comparison, here it has been recognized that a passive fluid-operated recuperation system may be even more environmentally friendly and efficient than an electrical recuperation system. The present idea overcomes a technical prejudice regarding the benefits of electric actuation, in particular the before-mentioned presumed beneficial combination of electric actuation and electric recuperation.

In an embodiment of the loader, the proximal end of the auxiliary actuator is mounted to the frame arrangement, e.g. to a front frame portion of the frame arrangement, coaxially with or below a connection of the lifting arrangement with the front frame portion. A coaxial arrangement may allow for a simpler and more cost-effective design, in particular if the auxiliary actuator shares a joint and/or axis with the lifting arrangement and/or the main actuator. A connection below the mounting position of the lifting arrangement may allow for a longer lever arm of the auxiliary actuator, rendering the recuperation more efficiently. Such an arrangement may also improve visibility.

In an embodiment of the loader, the main actuation system comprises a main actuator, which is connected to the lifting arrangement coaxially with the connection of the auxiliary actuator to the lifting arrangement. Alternatively, the main actuator is connected to the lifting arrangement at a position, which is distal to a connection position of the auxiliary actuator to the lifting arrangement. A coaxial arrangement may allow for a simpler and more cost-effective design, in particular with a shared joint and/or axis. The coaxial arrangement may further allow for a left-right arrangement of parallel and/or identical cylinders, namely a main cylinder and an auxiliary cylinder. A distal connection may provide the main actuator with a longer lever arm, rendering the main actuation system more efficient. Further, this embodiment allows for a compact loader design with good visibility.

In an embodiment of the loader, the auxiliary actuator is a cylinder connected with its rod end to the lifting arrangement and its cylinder end to the frame arrangement, e.g. to a front frame portion of the frame arrangement. Usually, the cylinder end is heavier. By its connection to the frame arrangement, overall movement of the auxiliary cylinder mass and thus energy loss may be reduced. Further, the diameter of the cylinder end may be larger than the rod end. Accordingly, arranging the rod end on the lifting arrangement may be less obstructive to the vision of the operator. The rod end of the auxiliary actuator may be mounted to the lifting arrangement at a position, which provides clearance to the front tire of the loader and good visibility to the corners of an equipment, e.g. a bucket, attached to the lifting arrangement in all intended operation states of the lifting arrangement, in particular also when the bucket is in a rolled back state. The cylinder may be configured as a fluid-operated cylinder, such as a hydraulic actuation cylinder. The auxiliary cylinder may be similar or identical to a main cylinder of the main actuation system. The amount of common parts may therefore be smaller and/or maintenance may be simpler.

In an embodiment of the loader, the lifting arrangement comprises a main arm with a pivot connector at its proximal end and the equipment connector at its distal end, the main actuation system being configured to pivot the main arm about the pivot connector such that the equipment connector is moveable between the lowered and lifted positions. The lifting arrangement further comprises a main arm support means for pivotably supporting the pivot connector of the main arm, wherein the main arm support means is movable in a direction, which includes at least a component in a front-rear direction with respect to the frame arrangement. The lifting arrangement may also comprise a guiding means, which is engaged to the main arm at a guided portion of the main arm positioned between the pivot connector and the equipment connector, wherein upon moving the lifting arrangement from the lowered to the lifted position, the guided portion is guided by the guiding means along a curved path such that the equipment connector follows a substantially vertical path between the lowered and lifted positions. The main arm support means, e.g. a proximal end thereof, may be mounted to the frame arrangement, e.g. the front frame portion of the frame arrangement. The front-rear direction may correspond to the forward-backward direction described above and may be perpendicular to the left-right direction. The lifting arrangement according to this embodiment provides a movement path of said equipment connector, which provides a decreased protruding distance in the intermediate position of said equipment connector which is positioned between the lowered position and the lifted position of said equipment connector. Based on this concept, the tilting moment exerted by the load acting on said equipment connector can be reduced when compared to the tilting moment acting on a construction machine having a main arm which provides a movement path for the equipment connector along a circular path with a radius which is defined by the distance between the pivot connector and the equipment connector.

In an embodiment of the loader, the auxiliary actuator is connected with its distal end to the main arm at a position, which is distal to the pivot connector and which is proximal to the guided portion, to which the guiding means is attached. Such an arrangement is compact while still allowing efficient recuperation. The main actuation system may comprise a main actuator which is connected to the main arm at a position, which is distal to the pivot connector and which is proximal to the guided portion. Such an arrangement is compact while still allowing for efficient lifting actuation of the lifting arrangement. In particular, the main actuator may be connected with its rod end to the main arm. In an embodiment, the main actuator is connected to the main arm at a position, which is distal to the connection position of the auxiliary actuator.

In an embodiment of the loader, a bucket or a lifting fork is mounted, preferably tiltably mounted, to the equipment connector. The tilting movement is preferably actuated by the main actuation system. Tilting may allow for a simple gathering and/or dumping of material. Further, tilting may allow for a configuration, in which the equipment has a constant orientation in space during lifting of the lifting arrangement from the lowered to the lifted position. For that purpose, the loader may comprise means to synchronize the tilting of the equipment with a lifting and lowering of the lifting arrangement. A bucket allows for efficient loading and/or unloading of loose material. A fork may allow to easily move compact goods, for example stored on a pallet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a wheel loader in perspective side view.

FIG. 2 shows in a schematic side view a front part for the wheel loader of FIG. 1 with a lifting arrangement in a lowered position.

FIG. 3 shows in a schematic side view the front part of FIG. 2 with the lifting arrangement in a raised position.

FIG. 4 shows in a schematic side view another front part for the wheel loader of FIG. 1 with a lifting arrangement in a lowered position.

FIG. 5 shows in a schematic side view the front part of FIG. 4 with the lifting arrangement in a raised position.

FIG. 6 schematically shows an auxiliary actuation system for the lifting arrangements of FIGS. 1-5.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a wheel loader 10 in a perspective side view. The wheel loader 10 comprises a front frame portion 12 and a rear frame portion 13, which are articulatingly interconnected for providing an articulating steering. The front frame portion 12 and the rear frame 13 portion may respectively comprise wheels 16. The wheels may be turnable around an essentially horizontal axis. Accordingly, the wheel loader 10 is steered by pivoting the two frame portions 12, 13 relatively to each other at their connection. Further, the wheel loader 10 comprises an operator's cab 11, which is attached to the rear frame portion 13. The axis of the wheels 16 of the front frame portion 12 defines a left-right direction, which may also be referred to as the transversal direction T. A front-rear direction F, which may also be referred to as the forward-backward direction, is defined as being perpendicular to the left-right direction while extending from the front to the back of the wheel loader 10. Accordingly, the forward-backward direction lies within the plane of the figures while the left-right direction is going into the paper plane. A top-bottom direction B is defined by gravity and is arranged perpendicular to the transversal direction T and the front-rear direction F.

FIG. 2 shows a front frame portion 12 with a lifting arrangement 18 in a lowered position according to a first embodiment of the invention, wherein said front frame portion 12 may be articulatingly mounted to the rear frame portion 13 of the wheel loader 10 of FIG. 1. For that purpose, the front frame portion 12 comprises mounting brackets 14, which can be engaged with complementary mounting bracket provided at the rear frame portion 13. A lifting arrangement 18 is mounted to the front of the front frame portion 12 with its proximal end. Proximal may be defined as being closer to the front frame portion 12. At its distal end, the lifting arrangement 18 has an equipment connector 23, presently in the form of through holes for pivotally mounting the bucket 20. Distal may be defined as farther away from the front frame portion 12. The lifting arrangement 18 shown in FIGS. 2 and 3 comprises a main arm 22, which is pivotably mounted with its proximal end to the front frame portion 12, the equipment connector 23 being provided at the distal end of the main arm 22.

In FIG. 2, the lifting arrangement 18 is shown in a lowered position where the equipment connector 23 and the bucket 20 are arranged in a lowered position close to the ground. In FIG. 3, the lifting arrangement 18 is shown in a raised or lifted position where the equipment connector 23 and the bucket 20 have been moved upwards away from the ground. Accordingly, the lifting arrangement 18 and the bucket 20 may be used to lift loose material, such as earth, from the ground, and dump it at a higher position, for example into a dump truck. The wheel loader 10 comprises a main actuation system 50. The main actuation system 50 comprises a battery 51, which is electrically connected to an electric motor 52, the electric motor 52 driving a hydraulic pump 53. Thus, only via the electrical energy stored in the battery 51, the hydraulic pump 53 may be driven. The hydraulic pump 53 may be part of a hydraulic system to power a main hydraulic cylinder 24 for lifting the main arm 22 between the lowered position shown in FIG. 2 to the lifted position shown in FIG. 3. The main cylinder 24 is pivotably mounted with its cylinder end to the front frame portion 12 and with its rod end to the main arm 22. By pressurizing the main cylinder 24 with hydraulic fluid via the hydraulic pump 53, the main actuation system pivots the main arm 22 and thus the equipment connector 23 relative to the front frame portion 12 from the lowered to the lifted position. With a depressurization, the lifting arrangement 18 and thus the equipment connector 23 may be lowered again.

In addition, the main actuation system 50 comprises a hydraulic tilting cylinder 26, which may be actuated hydraulically via the hydraulic pump 53. The hydraulic tiling cylinder 26 is pivotably connected with its cylinder end to the front frame portion 12. Its rod end is connected to an end portion of a link element 28, said link element 28 being pivotably mounted to the main arm 22 with a center portion thereof. At an opposite end, the link element 28 is connected to the bucket 20 via a further link element. By pressurizing and depressurizing the tilting cylinder 26 via the hydraulic system, the bucket 20 may be tilted relatively to the main arm 22 for loading and unloading of the bucket 23, respectively. Furthermore, the main actuation system 50 may drive the wheels 16 of the wheel loader 10 and/or actuate a steering cylinder (not shown) for pivoting the front frame portion 12 with respect to the rear frame portion 13.

Further, the wheel loader 10 comprises an auxiliary actuation system 60 for storing energy during lowering of the equipment connector 23 and for using the stored energy to support the main actuation system 50 in raising of the equipment connector 23. The auxiliary actuation system 60 is schematically shown in FIG. 6. The auxiliary actuation system 60 comprises an auxiliary actuator in the form of a fluid-operated auxiliary cylinder 30. The lifting arrangement 18 and the auxiliary actuation system 60 may also be referred to as a counter-balanced boom. The auxiliary actuation system 60 may be separate from and autonomous to the main actuation system 50. For example, it may comprise an accumulator 61 that stores released potential energy during lowering of the lifting arrangement 18 due to a pressurization of its fluid system when the auxiliary cylinder 30 is retracted. This stored energy or pressure may be used to extend the auxiliary cylinder 30 during raising of the lifting arrangement 18, thus supporting such an upward movement. In the present embodiment, the auxiliary actuation system 60 is a hydraulic system and is operated with hydraulic fluid. Alternatively, it may also be a pneumatic system that is operated by gas, e.g. nitrogen.

FIG. 6 illustrates in a schematic view the connection of the auxiliary cylinder 30 with accumulator 61. As can also be taken from FIG. 6, the auxiliary actuation system 32 does not necessarily require an active control and/or any valves. Accordingly, the system is simple, easy to service and cost-effective. However, a valve 62 and optionally also a control unit 63 could be added to provide depressurization of the auxiliary actuation system 60 after shutdown of the wheel loader 10. Alternatively or additionally, the valve 62 and control unit 63 could also serve to initially pressurize the auxiliary actuation system 60 via the hydraulic pump 53, which was described above, and a fluid connection line 64. Specifically, when turning on the wheel loader 10, the control unit 63 might be configured to open the valve 62, thereby pressurizing the auxiliary actuation system with hydraulic fluid from the main hydraulic system, i.e. via the hydraulic pump 53. Once pressurized, the control unit 63 is configured to close the valve 62 and keep it closed during operation of the auxiliary actuation system 60. Likewise, when the wheel loader 10 is turned off, the control unit 63 may be configured to open the valve 62 again to de-pressurize the auxiliary actuation system 60.

The auxiliary cylinder 30 is connected with its distal rod end to the main arm 22 proximal to a connection of the cylinder 24 of the main actuation system 50 to the main arm 22. Such an arrangement is efficient as it does not block the view of an operator on the bucket 20 and the equipment connector 23, especially in a raised position and/or in comparison to an auxiliary actuator connected to the main arm 22 distal to the main cylinder 24. The auxiliary cylinder 30 may be connected to the top portion of the main arm 22 for providing a large stroke between the lowered and raised positions of the main arm 22. The proximal cylinder end of the auxiliary cylinder 30 is connected to the front frame portion 12. For example, it may be connected to the same joint and/or axis as the main cylinder 24, resulting in a compact and cost-effective design.

Such an arrangement may be referred to as coaxial arrangement. Further, the auxiliary cylinder 30 is connected at a transversal side to both the main arm 22 and the front frame portion 12. In other words: the auxiliary cylinder 30 is connected to the side surface of the lifting arrangement 18 and the front frame portion 12 in a left-right direction T, in particular sideways to a plane defined by the movement between the lifted and the lowered positions of the main arm 22. Such an arrangement may allow for the before mentioned coaxial arrangement. Further, such an arrangement is particularly beneficial for the vision of the operator when controlling the wheel loader 10. For example, unlike an arrangement above the main arm 22, the auxiliary cylinder 30 does not or at least less block a view of the operator on the bucket 20, e.g. in the lowered position. Overall, wheel loader 10 operations are therefore easier to control.

To illustrate the working principal of the auxiliary hydraulic actuation system 60, FIG. 3 shows a raised position of the main arm 22 and FIG. 2 shows a lowered position of the main arm 22. As can be seen in FIG. 3, in the position in which the auxiliary hydraulic actuation cylinder 30 is fully extended, the main arm 22 is raised. In that position, the accumulator 61 and the overall auxiliary hydraulic actuation system 60 is not pressurized, in particular relative to an ambient pressure. When lowering the main arm 22, the auxiliary hydraulic cylinder 30 is retracted. Due to this retraction, there is a pressure increased in the auxiliary hydraulic actuation system 60, which stores the freed potential energy during lowering of the main arm 22 in the accumulator 61. When lifting the main arm 22 from the lowered position shown in FIG. 2 to the raised position of FIG. 3, the thus stored potential energy may be used to extend the auxiliary hydraulic cylinder 30, thus supporting raising of the main arm 22. Therefore, overall required power output to raise the main arm 22 may be reduced. The operation of the main hydraulic actuator 24 shown in FIGS. 2 and 3 during raising of the main arm 22 is supported by the auxiliary hydraulic cylinder 30.

FIGS. 4 and 5 show another embodiment of a wheel loader 10. Overall, its operation and actuation systems are similar or even identical to the operation and system described for the embodiment shown in FIGS. 2 and 3. FIG. 4 shows a lowered position and FIG. 5 a raised position. Except for the differences described below, the embodiment shown in FIGS. 4 and 5 is configured as the embodiment shown in FIGS. 2 and 3. In particular, the embodiment shown in FIGS. 4 and 5 comprises a main arm actuation system 50 and an auxiliary actuation system 60 as well as an arrangement for tilting the bucket 20 which are configured as described in connection with FIGS. 2 and 3 except for the below differences. The same reference numbers designate identical or like parts.

The lifting arrangement 18 of the embodiment shown in FIGS. 4 and 5 is different from that described in connection with FIGS. 2 and 3. As can be taken from the line 32 in FIG. 3, the equipment connector 23 at the distal end of the main arm 22 of the wheel loader 10 moves along a circular path when moving the lifting arrangement 18 from the lowered position of FIG. 2 to the lifted position of FIG. 3. This is due to the rigid arm 22 having a constant length and being supported at a stationary section of the front frame portion 12. By comparison, and as can be taken from the line 34 in FIG. 5, the equipment connector 23 of the wheel loader 10 shown in FIGS. 4 and 5 moves along a substantially vertical path when moving the lifting arrangement 18 from the lowered position of FIG. 4 to the lifted position of FIG. 5. This is possible due to a different and unique design of the lifting arrangement, which will be described below.

Said lifting arrangement 18 of FIGS. 4 and 5 comprises a main arm 22 with a pivot connector 36 at its proximate end thereof and the equipment connector at its distal end. The lifting arrangement 18 further comprises a main arm support means 38 for pivotably supporting the pivot connector 36 of the main arm 22. The main arm support means 38 is movable in a direction, which includes at least a component in a front-rear direction F with respect to the front frame portion 12. The proximal end of main arm support means 38 is pivotably supported by the front frame portion 12, and the distal end of the main arm support means 38 pivotably supports the proximal end of the main arm 22. The lifting arrangement 18 further comprises a guiding means 40, one end of which being engaged to the main arm 22 at a guided portion of the main arm 22 positioned between the pivot connector 36 and the equipment connector 23, and the other end of the guiding means 40 being supported by the front frame portion 12. Upon moving the main arm 22 from the lowered position of FIG. 4 to the raised position of FIG. 5 with the main arm actuation system 50, the guiding means 40 guides the guiding portion of the main arm 22 along a circular path, thereby moving the main arm support means 38 in the front-rear direction F. Therefore, the equipment connector 23 is moved along a substantially vertical trajectory 34.

Both the main cylinder 24 and the auxiliary cylinder 30 are connected to the main arm 22 between the guided portion and the pivot connector 36 thereof. This prevents unnecessarily blocking of the vision of the operator and results in an efficient and compact design. Further, the main cylinder 24 is mounted to the front frame portion 12 at a lower and more forward position than the auxiliary cylinder 30 to better support the main arm 22. Again, the auxiliary cylinder 30 is arranged at a transversal side of the main arm 22 and thus the lifting arrangement 18, i.e. at side surface of the main arm 22 in left-right direction T, with the above-noted advantageous effects.

REFERENCE SIGNS

-   10 wheel loader -   11 cab -   11.1 front window -   12 front frame portion -   13 rear frame portion -   14 mounting brackets -   16 wheel -   18 lifting arrangement -   20 bucket -   22 main arm -   23 equipment connector -   24 main cylinder -   26 tilting cylinder -   28 link element -   30 auxiliary cylinder -   32 moving trajectory -   34 moving trajectory -   36 pivot connector -   38 support means -   40 guiding means -   50 main actuation system -   51 battery -   52 electrical drive -   53 hydraulic pump -   60 auxiliary actuation system -   61 accumulator -   62 valve -   63 control unit -   64 hydraulic line 

1. A loader including a frame arrangement, the frame arrangement comprising a front frame portion and a rear frame portion articulatingly interconnected for providing an articulating steering, the loader comprising: a lifting arrangement mounted to the frame arrangement and comprising an equipment connector at a distal end of the lifting arrangement; a main actuation system for pivoting the equipment connector relative to the frame arrangement such that the equipment connector is movable between a lowered position and a lifted position; and an auxiliary actuation system for storing energy during lowering of the equipment connecter and for using the stored energy to support the main actuation system in raising of the equipment connecter; wherein the auxiliary actuation system comprises an auxiliary actuator connected at it a proximal end to the frame arrangement and connected at a distal end to the lifting arrangement at a transversal side of the lifting arrangement.
 2. The loader according to claim 1, wherein the distal end of the auxiliary actuator is arranged below an operator's cab of the loader and/or a front window of the operator's cab when the equipment connector is in the lowered position.
 3. The loader according to claim 1, wherein the auxiliary actuation system is a fluid-operated actuation system comprising an accumulator for storing energy.
 4. The loader according to claim 1, wherein the auxiliary actuation system is provided separately from the main actuation system and is configured to store energy and to support raising of the equipment connector completely autonomously without interaction with the main actuation system.
 5. The loader according to claim 1, wherein the main actuation system is an electrical system with an electrical power storage unit and an electrical drive configured to actuate movement of the equipment connector between the lowered position and the lifted position, and wherein the main actuation system is configured to actuate articulation of the front frame portion and the rear frame portion with respect to each other and/or to actuate driving of the loader.
 6. The loader according claim 5, wherein the main actuation system comprises a main hydraulic system configured to actuate movement of the equipment connector between the lowered position and the lifted position, and wherein the main hydraulic system is configured to be powered by the electrical drive.
 7. The loader according to claim 1, wherein the proximal end of the auxiliary actuator is mounted to the front frame portion coaxially with or below a connection of the lifting arrangement to the front frame portion.
 8. The loader according to claim 1, wherein the main actuation system comprises a main actuator connected to the lifting arrangement coaxially with or distal to a connection of the auxiliary actuator to the lifting arrangement.
 9. The loader according to claim 1, wherein the auxiliary actuator is a cylinder connected at a rod end to the lifting arrangement and at a cylinder end to the front frame portion.
 10. The loader according to claim 1, wherein: the lifting arrangement comprises a main arm with a pivot connector at a proximate end and the equipment connector at a distal end; the main actuation system is configured to pivot the main arm about the pivot connector such that the equipment connector is moved between the lowered position and the lifted position; and the lifting arrangement further comprises: a main arm support means for pivotably supporting the pivot connector of the main arm, wherein the main arm support means is movable in a direction which includes at least a component in a front-rear direction with respect to the frame arrangement; and a guiding means engaged to the main arm at a guided portion of the main arm positioned between the pivot connector and the equipment connector, wherein upon moving the equipment connector with the main actuation system from the lowered position to the lifted position, the guided portion is guided by the guiding means along a curved path such that the equipment connector follows a substantially vertical path.
 11. The loader according to claim 10, wherein the auxiliary actuator is connected to the main arm at a position distal to the pivot connector and proximal to the guided portion.
 12. The loader according to claim 10, wherein the main actuation system comprises a main actuator connected to the main arm at a position distal to the pivot connector and proximal to the guided portion, and wherein the position is distal to a connection of the auxiliary actuator to the main arm.
 13. The loader according to claim 1, wherein a bucket or a lifting fork is tiltably mounted to the equipment connector.
 14. The loader according to claim 1, wherein the proximal end of the auxiliary actuator is connected to the front frame portion below an operator's cab and/or a front window of the operator's cab. 